1. Field of the Invention
The invention is related to earplugs and, more particularly, to earplugs suitable for use by an underwater diver.
2. Description of the Prior Art
Self-contained underwater breathing apparatus (SCUBA) is widely used for military, commercial, and recreational diving. Instead of the heavy sealed diving helmets and clumsy air lines still used for certain diving applications, SCUBA equipment provides greatly increased convenience and freedom of movement. The basic equipment includes one or more tanks of pressurized air, a pressure regulator, and a mouthpiece connected by flexible hose to the regulator and pressurized tank. With the mouthpiece inserted into the mouth of a submerged diver, the regulator provides air, on demand, at the ambient pressure of the surrounding water. Transfer of air at the pressure of the surrounding water through the Eustachian tube allows air pressure in the middle and inner ear regions to balance the water pressure on the outer side of the tympanic membrane, or eardrum. This balancing of pressure on either side of the eardrum is called equalization.
The presence of water in the auditory meatus in direct contact with the eardrum can also introduce dirt, bacteria, and other contaminants to the outer ear region. Furthermore, failure to achieve equalization (due to nasal congestion, equipment failure, or fault of the diver) can result in an inward rupture of the eardrum, permitting the cold water and contaminants to enter the middle and inner ear regions. The immediate problem caused by inundation of these regions is vertigo, the inability to sense up-and-down orientation. This in turn may cause the diver to take irrational action, such as descending to even greater depths or ascending without exhaling, resulting in ruptured lungs. This risk is most likely and most dangerous for the novice diver.
Infection is a serious subsequent problem which can develop from inundation of the inner and middle ear regions with contaminated water. Although such infections are usually treatable, they can cause deafness as well as temporary or permanent inability to dive. In addition to the personal disability of the diver, this can result in serious economic and tactical consequences through loss of manpower resources in commercial and military situations.
Existing earplugs are designed to protect the auditory meatus and eardrum from noise, water, and pressure waves by fixedly sealing the outer end of the auditory meatus. They form a fixed volume of air between the earplug and the eardrum which prevents equalization. The fixed volume of air remains at essentially atmospheric pressure while increasing water pressure during the diver's descent causes a corresponding increase in air pressure in the inner and middle ear regions. The eardrum may eventually rupture in an outward direction.
Although other existing earplugs provide labyrinths or orifices to allow attenuated noise and pressure waves into the auditory meatus, they fail to exclude the entrance of water thereto, and thus give rise to the aforementioned problems of contamination, vertigo, and infection.
It would therefore be desirable to provide an earplug suitable for use in underwater diving, particularly to the depths achievable with SCUBA equipment. This earplug should allow proper pressure equalization during normal conditions and prevent contamination of the auditory meatus and inner and middle ear regions under all conditions, including those resulting from a ruptured eardrum.